Method for preparing imines



Patented Oct. 19, 1954 UNITE S ATENT OFFICE METHOD FOR PREPARING IMINEScorporation of Delaware Ne Drawing. Application November 28, 1952,Serial No. 323,161

11 Claims.

This invention relates to the preparation of imines. More particularly,the invention relates to a novel method for preparing new imines byreacting a ketimine with certain carbonylic compounds, and to certainnovel unsaturated imines prepared. thereby.

Specifically, the invention provides a new and highly efiicient processfor preparing new imines, such as aldimines, cyclic ketimines andketosubstituted ketimines, which comprises contacting a ketimine with acarbonylic compound of the group consisting of aldehydes and betadiketones and then separating the desired imine product from thereaction mixture. The invention further provides certain novelunsaturated imines having a conjugated system of double bonds involvingthree carbon atoms and the imine nitrogen atom which are produced by theabove-described process.

This application is a continuation-in-part of my application, Serial No.17,797, filed March 29, 1948, now abandoned.

The expression aldimine as used herein and in the appended claims refersto those compounds which are obtained by replacing the oxygen atom inthe formyl group of an aldehyde with a =NR radical wherein R is anorganic radical and the expression ketimine as used herein and in theappended claims refers to those compounds which are obtained byreplacing the oxygen atom of the oxo group of a ketone with the said =NRradical.

Imines have heretofore been prepared by condensing an amino compoundwith a ketone or aldehyde, the reaction going forward in the presence ofa condensation catalyst which is usually of the acid type. Many imines,however, cannot be prepared by this method, or at least the yieldthereof is poor.- In other cases, While some of the desired ketiminesand aldimines are obtained by condensing the amino and carbonylicreactants, the amount of various byproducts formed is so large that theprocess must be considered impractical of operation.

It is, therefore, an object of the invention to provide an improvedprocess for preparing imines. It is a further object to provide a methodfor preparing aldimines, cyclic ketimines and keto-substituted ketiminesby reacting a dissimilar ketimine with an aldehyde or beta diketone. Itis a further object to provide a method whereby a ketimine and aldehydeare reacted to form an aldimine. It is a further object to provide amethod for preparing novel unsaturated imines by reacting a ketiminewith an unsaturated ketimine. It is a further object to provide a methodwhereby a ketimine and beta diketone are reacted to form aketo-substituted ketimine. It is a further object to provide a methodfor preparing imines that can be accomplished without the use ofcatalytic material. It is a further object to provide novel unsaturatedimines having a conjugated system of double bonds involving three carbonatoms and the imine nitrogen atom. Other objects and advantages of theinvention will be apparent from the following detailed descriptionthereof.

It has now been discovered that these and other objects may beaccomplished by the process of the invention which comprises contactinga lretimine with a carbonylic compound of the group consisting ofaldehydes and beta diketones and separating the desired imine prod notfrom the reaction mixture.

When the compound reacted with the ketimine in the above-describedprocess is an aldehyde, the resulting product will be an aldimine formedby the replacement of the radical which is attached to the nitrogen atomthrough a double bond in the ketimine molecule for the radical which isattached through a double bond to the oxygen atom in the formyl group ofthe aldehyde. This reaction may be exemplified bythe following equationshowing the preparation of N-(l-butylidene) propylamine by reacting N-(2-propylidene) propylamine with butyralde- If the aldehyde reactant isan alpha,betaethylenically unsaturated aldehyde, such as methacrolein orcrotonaldehyde, the resulting product will be an unsaturated aldirninehaving a conjugated system of double bonds involving three carbon atomsand the imine nitrogen atom. The production of these unsaturatedaldimines may be exemplified by the following equation showing theproduction of N-(methallylidene) hexylamine by reacting'methacroleinwith N- l-methylpent-2-ylidene) hexylamine:

If the aldehyde reactant is acrolein or an alpha-substituted acrolein,such as methacrolein, and the ketimine reactant has the NR 4L groupattached through free bonds of the carbon atom to two separate aliphaticcarbon atoms bearing two active hydrogen atoms, .the reaction mixturewill contain, in addition to the above-described unsaturated :aldimines,,an unsaturated cyclic ketimine having aconjugated system of doublebonds involving three carbon atoms and the imine nitrogen atom. In fact,with acrolein, the reaction mixture contains a very large amount of thistype of ketimine. These particular cyclic ketimine by-products arebelieved to be formed by a Michael-type addition of 'one of the carbonatoms attached to :the imino group in the ketimine molecule with theethylenic linkage of the unsaturated aldehyde, and then theterminalaldehyde group condenses on the remaining carbon atom attachedto the imino group in the ketimine molecule by aldol condensation :toform the cyclic ketimine. This reaction .may be exemplified by thefollowing equation showing the production of .N-(1,3-dimethylbultyl) 2isopropylcyclohexeneimine by reacting acrolein with.N-(1,3-dimethylbutylidene) hexylamine:

NCaHm and/or H H1O CH acetylacetone:

II CH3 CHrC-CH:

CaH1N= o:

Ha CHa ll 'OHz-C-CH: on;

CaH7N=$ O:

CH: CH:

The above-described process of the invention 1s unobvious and could nothave been foreseen.

ucts, however, are not uncommon in the present process. Particularlysurprising is the fact that the unsaturated aldehydes, such as acrolein,

inethacrolein and crotonaldehyde, react with the ketimine to produce theabove-described unsaturated aldimines and cyclic ketimines having theconjugated-system of double bonds involving the three carbon atoms andterminal nitrogen atom. Such a system is new and believed to bedifficult if not impossible to prepare.

The ketimines used in the process of the invention are :those of theformula wherein R, R1 and R2 are organic radicals other than hydrogen,and are preferably hydrocarbon radicals, such as aliphatic and aromatichydrocarbon radicals. For clarity in understanding the invention, theketimines will be described herein and in the appended claims assubstituted amines. Thus, when R, R1 and R2 in the abovedescribedformula are hydrocarbon radicals, the ketimines may be genericallydescribed as N- (hydrocarbylidene) hydrocarbylamines wherein thehydrocarbylidene group is attached to the nitrogen atom through'twovalences of a secondary carbon atom. The expression hydrocarbylidene asused herein and-in the appended claims refers to a hydrocarbon radical,the free bond of which consists of two valences of a single carbon atom.The expression hydrocarbyl as used herein and in the appended claimsrefers to a hydrocarbon radical, the free bond of which consists-of asingle valence-of a single carbon-atom.

Examples of ketimines that may be usedin the present process includeN-(Z-butylidene) amylamine, N-(2-butylidene) 1-(2-chlorobutyl) amine,N-(Z-isooctylidene) phenylamine, 'N-(2- pentylidene) nonylamine, N (3cyclohexyl -2 butylidene) LB-dimethylbutylamine, N-(2-hex- 4 -enylidene)1,3 diethylbutylamine, N (4 phenyl 2 hexylidene) cyclohexylamine, N (4hexyn-Z-ylidene) 1,3-diethylhexylamine, N-(3- pentylidene)naphthylamine, N-(Z-octylidene) cyclohex-3-enylamine and N-(2-decylidene) 2,4- hexadienylamine.

Preferred ketimines to be used in the present process are theN-(alkylidene) alkylamines, the N-(alkylidene) alkenylamines, theN-(alkylidene) cycloalkylamines, the N- (alkylidene) arylamines, and theN-(alkylidene) alkarylamines, the N-(arylalkylidene) alkylamines, theN-(arylalkylidene) alkenylamines, the N-(arylalkylidene)cycloalkylamines, the l. -(ary1alkylidene) arylamines and theN-(arylalkylidene) alkarylamines, the alkylidene and arylalkylidenegroups in the afore-described compounds being joined to the nitrogenatom through two valences of a singlesecondary aliphatic carbon atom.Examples of these preferred ketimines include N-(Z-butylidene)octylamine, N-(3- octylidene) amylamine, N-(B-hexylidene allylamine,N-(2-butylidene) hex-Z-enylamine, N- (2-pentylidene) phenylamine,N-(3l-hexylidene) cyclohexylamine, f N- (Z-pentylidene) 2-methy1-phenylamine, N-(2-decylidene) allylamine, N- (Z-butylidene)4-isopropylphenylamine, N-(3- phenyl-2-butylidene) butylamine,N-(3-phenyl- 3 hexylidene) 1,3 diethylbutylamine, N (3phenyl-S-hexylidene) allylamine, N-(Z-phenyl- 3-hexylidene)cyclohexylamine, N-(3phenyl-3- octylidene) phenylamine andN-(2-toluyl-3- hexylidene) 4,-isopropylphenylamine.

Of special interest, particularly because of the ease of operation ofthe process, are the ketimines possessing an alkylidene group attachedto the nitrogen atom, such asthe N-(alkylidene) alkylamines, theN-(alkylidene) alkenylamines, the N-(alkylidene) cycloalkylainines andthe N-(alkylidene) arylamines, and particularly those aliphaticketimines of the formula R2 wherein R, R1 and R2 are alkyl radicals,preferably containing from 1 to 12 carbon atoms, and more particularlyfrom 1 to 8 carbon atoms.

The ketimines described above may be prepared by a variety of methodsknown to the art. Many of them may, for example, be prepared by theconventional method of reacting a ketone with an amine such as describedin U. S. 2,533,723. Many of the ketimines may also be prepared by amethod related to the presently described process which is described andclaimed in my copending application Serial No. 323,162, filed November28, 1952.

The aldehydes used in the process of the invention may be aliphatic,cycloaliphatio, aromatic or heterocyclic and may be saturated orunsaturated and possess straight or branched chains. Examples of suchaldehydes include propionaldehyde, butyraldehyde, isobutyraldehyde,,valeraldehyde, caproic aldehyde, heptoic aldehyde, methacrolein,acrolein crotonaldehyde, nicotinaldehyde, cinchoninaldehyde,2-pyrancarboxaldehyde, tetrahydropyran 2 carboxaldehyde, Z-furaldehyde,cinnamaldehyde, p-tolualdehyde, benzaldehyde, l-naphthaldehyde, 1-cyclohexene-l-carboxaldehyde, -butyl-l-cyclohexene-l-carboxaldehyde,l-cyclopentene-l-carboxaldehyde, ZA-heptadiene-l-carboxaldehyde and2-isopropyl-l-cyclopentene-l-carboXalde hyde.

Preferred aldehydes to be used in the process comprise the unsubstitutedhydrocarbon aldehydes, i. e., the mono-formyl substituted hydrocarbons,such as butyraldehyde, valeraldehyde, caproic aldehyde, caprylicaldehyde, crotonaldehyde, inethacrolein, 2,4-heptadiena1, 3,5-octadienal, cyclohexanecarboxaldehyde,3-methyl-1-cyclohexene-2-carboxaldehyde, benzaldehyde and-isobutylbenzaldehyde.

Of the above group those that are particularly preferred are thearomatic aldehydes, i. e., the mono-formyl substituted aromatichydrocarbons, which preferably contain a single G-membered aromatic ringand no more than 18 carbon atoms, the saturated aliphatic aldehydes, i.e., the monoformyl substituted aliphatic hydrocarbons, which preferablycontain no more than carbon atoms, and the substituted acroleins havinga hydrocarbon radical attached to the alpha carbon atom, the beta carbonatom or both the alpha and beta carbon atoms, the hydrocarbon radicalpreferably containing no more than 8 carbon atoms. The aromaticaldehydes may be exemplified by benzaldehyde, tolualdehyde,-isohexylbenzaldehyde, 4-tert-butylbenzaldehyde, 4-

isopropylbenzaldehyde, 2 methyl 4 isopropylbenzaldehyde and3-propyll-isoheptylbenzaldehyde. The saturated aliphatic aldehydes maybe exemplified by butyraldehyde, valeraldehyde, caproic aldehyde,propionaldehyde, caprylic aldehyde, capric aldehyde, lauric aldehyde,cyclohexanecarboxaldehyde, methylcyclohexanecarboxaldehyde,cyclopentanecarboxaldehyde, 2,3- dimethylcyclopentanecarboxaldehyde, 4isooctylcyclohexanecarboxaldehyde, 3,5,5-trimethyloctanal,3-butyldodecana1 and 3,5-diisopropyldecanal. The substituted acroleinsmay be exemplified by alpha-butyl acrolein, beta octyl acrolein,alpha,beta-dibutyl acrolein, alphaethyl acrolein and alpha-isobutylacrolein.

If the process is to be used to prepare unsaturated aldimines having aconjugated system of double bonds involving three carbon atoms and theimine nitrogen atom, the aldehyde is preferably analpha,beta-unsaturated aliphatic aldehyde, and more preferably one ofthe above-described alpha, beta or alpha and beta-substituted acroleins,such as the alpha, beta and alpha and beta alkyl-substituted acroleinswherein the alkyl radical contains no more than 5 carbon atoms. If theprocess is to be used mainly for the preparation of the above-describedunsaturated cyclic ketimines, the aldehyde reactant is preferablyacrolein or any one of the above-described alphasubstituted acroleins asthe alpha-alkyl-substituted acroleins wherein the alkyl radical containsno more than 5 carbon atoms.

Coming under special consideration, particularly because of the ease ofoperation and fine yields of products, are the aliphatic aldehydes suchas those of the formula wherein R3 is an aliphatic hydrocarbon radicalcontaining no more than 10 carbon atoms. Alkanals, cycloalkanals,alkenals and cycloalkenals and preferably the Z-alkenals and2-cycloalkenals, containing no more than 8 carbon atoms are ofparticular value in the process.

The beta diketones used in the process to prepare the keto-substitutedketimines are those compounds having two OX0 groups, i. e., two

groups, separated by a single carbon atom. Such compounds may possessaliphatic, aromatic or heterocyclic radicals, may be saturated orunsaturated and may possess straight or branched chains. Examples ofsuch diketones include 2,4- pentanedione, 2,4-octanedione,3,5-hexanedione, 3,5-didecanedione, 2,3-diethyl-4,6-d0decanedione, 2ethylhexanedione 3,5,6 phenyl 2,4: hexanedione,Z-acetyl-l-cyclohexanone, 2,3-dibutyl- 4,6-decanedione and6-decenedione3,5.

Preferred diketones to be used in the process comprise the hydrocarbylbeta dilietones, i. e., the beta diketo-substituted hydrocarbons, suchas those of the formula wherein R is a hydrocarbon radical, as2,4-pentanedione, 2,4-heptanedione, 2,4-decanedione, 3,5 hexanedione,2,3 diethyl 4,6 dodecanedione and 6-phenyl-2,4-hexanedione. Of thisgroup, those that are particularly preferred are the diketo-substitutedaliphatic hydrocarbons, such as the alkanediones, the alkenediones, the

7 cycloalkanediones. and thecycloalkenediones; which preferably containnomore than 12 carbon atoms.

Of'special interest, particularly because of the ease of operation ofthe process are the diketones of the formula wherein one R'is analiphatic open-chain hydrocarbon radical containing from 1 to 3 carbonatoms and the other R'is an aliphatic open-chain hydrocarbonradical-containing no more than 6 carbon atoms. Alkanediones andalkenediones containing no more than 8.carbon atoms are of special valuein theprocess.

In the operation of the process, any of the above-described ketiminesmay be reacted with any of the above-described carbonylic com-- pounds.As indicated above, the product obtained in each case will depend on thetype of carbonylic compound used as the reactant. If the aldehydes areused as reactants, the products will be aldimines. If the aldehyde is analpha, beta-ethylem'cally unsaturated aldehyde and if the aldehyde isacrolein or an alpha-substituted acrolein, the product will contain, inaddition to the aldimines, an unsaturated cyclic ketimine. Thus,acetaldehyde may be reacted with N-(- methylpent-Z-ylidene)isopropylamine to produce N-(ethylidene) isopropylamine, butyraldehydemay be reacted with N-(Z-propylidene) propylamine to produce N (1butylidene) propylamine, methacrolein may be reacted with N (1,3dimethylb-utylidene) 1,3 dimethylbutylamine to produceN-(l-methylallylidene) 1,3-dimethylbutylamine as well as some N-(1,3-dimethylbutyl) 2 isopropyl 4 methycyclohexeneimine and crotonaldehydemay be reacted with N (1,3 dimethyl'butylidene) 1,3 dimethylbutylamineto produce N-(l-crotylidene) 1,3-dimethylbutylamine,

When the diketones are used as the carbonylic reactant, the productswill be keto-substituted ketimines. Thus, acetylacetone may be reactedwith N-(2-propylidene) isopropylamine to produce 4 isopropylimino 2pentanone, 2,4- heptanedione may be reacted with N-(2-butylidene)hexylamine to produce 2-hexylimino-dheptanone and acetylacetone may bereacted with N-(2-propylidene) octylamine to produce-octylimino-2-pentanone.

The reaction between the aforedescribed ketimines and carbonyliccompounds is accomplished by merely bringing the components together ina suitable reaction chamber. The ketimines and the carbonylic compoundsmay be combined with either one or both in stoichiometric excess, suchas from 1 to 3 mols of the one compound for every mol of the other.Generally speaking, however, the most advantageous results in respect tothe yield of imine product are obtained through use of the reactants inthe mol for mol proportions which are theoretically required.

The reaction between the ketimine and carbonylic compounds is exothermicin character andproceeds without the application of external heat.However, in some instances it is desirable to apply some heat in orderto increase the speed of the reaction. It may also be desirable in someinstances to apply sufficient heat to remove. one or more of theproducts of reaction by distillation. Such a removal, however, isnotessential toa successful operation of the process. Imgeneral,temperatures used in the process may'vary from 30 C. to 200 C.', andmore preferably from 50 C. to C.

The reaction is preferably conducted at atmospheric pressure, but insome instances.- it may be desirable to use superatmosphericorsubatmospheric pressure.

The process may be conducted in the presence or absence of catalyticmaterial. In someimstances, it may be desirable to speed thev reactionby adding catalytic material, such as an acid-acting salt, as zincchloride, as well as acids such as hydrochloric and sulfuric acid,orthophosphoric acid and benzene-sulfonic acid. In general, an amount ofcatalyst ranging from 0.01% to 5%, and preferably from 0.5% to 1%, basedon the weight of the ketimine reactant, represents a suitable amountwhen carrying on the process of the invention in the liquid phase and ina batchwise manner. However, it should be noted that in the preferredpractice of the invention, no catalyst is employed.

The process of the invention may be carried out in the presence orabsence of solvents or diluents. In general, however, solvents ordiluents are not employed as both the ketimine, aldehyde and diketonereactants as well as the imine and ketone products, are normally liquidat the temperature employed. If a solvent or diluent is used, as toplace the mixture in a. more fluid condition, it should be a materialwhich is both liquid and inert under the prevailing reaction conditions.Materials which may be used for this purpose are, for example,isooctane, xylene, dioxane and diethylene lycol diethyl ether.

The time required for the reaction will vary over a considerable rangedepending on thetype of reactants used in the process, use of catalyticmaterials as described hereinafter and the temperature selected. In mostinstances, at the lower temperatures and in the absence of catalyticma-, terial, the reaction may take considerable time, e. g., from 1 to20 hours. If higher temperatures and/or catalysts are used, thereactionmay generally be accomplished in a much shorter period; e. g.,from 1 to 5 hours.

After the reaction is complete, the imine product is separated from theother components of the mixture of which it forms a part by anyconvenient manner. A preferred separation method is that of fractionaldistillation, at reduced pres:- sure if necessary, as the imines arenormally stable materials that can be 'volatilized Withoutdecomposition. However, other methods of-sepairation may be used.

The process of the invention may be carried out in a batchwise,continuous or semi-continuous manner. For batch treatment, the ketimineand carbonylic reactants are preferably added to a suitable vessel wherethey are allowed to react and then at the completion of the reaction,the desired imine product is removed from the mixture, preferably bydistillation. If a continuous operation is desired, it is preferablyaccomplished by adding the ketimine and carbonylic compound continuouslyor intermittently to the reaction vessel as the reaction progressesandcontinuously removing the imine product and/or. ketone bydistillation.

To illustrate the manner inwhich the invene tion may be carried out, thefollowing examples are given. It is to be understood, however, that theexamples are for the. purpose of illustration and' the invention is notto be regard ed a's limited to any of the specific materials describedtherein.

Example I This example illustrates the reaction between a ketimine and abeta diketone to produce a keto-substituted ketimine and a new ketone.

Approximately one mol of N-(2-propylidene) isopropylamine was combinedwith approximately 1 mol of acetylacetone in a glass reaction flask atroom temperature. These materials reacted rapidly and in 10 minutes thetemperature had increased to 60 C. After the reaction was complete, themixture was distilled to recover 0.77 mol of4-isopropylimino-2-pentanone and 0.95 mol of acetone. The4-isopropylimino-2-pentanone had a boiling point of 104 C. to 105 C. at20 mm. Hg.

In a similar manner, 5-butylimino-3-hexanone is produced by reactingN-(Z-butylidene) butylamine with 2,4-hexanedione and 6-hexylimin0-4-heptanone is produced by reacting N-(2- butylidene) hexylamine with2,4-heptanedione.

Example II This example illustrates the reaction between a ketimine andan aldehyde to produce an aldimine and a new ketone.

Approximately 2 mols of N -(1,3-dimethylbuty1- idene) isopropylamine wascombined with 2 mols of acetaldehyde in a glass reaction flask and themixture distilled. At 53 C. to 1 0. there was collected 1.47 mols ofN-(ethylidene) isopropylamine and 1.95 mols of methyl isobutyl ketone.

In a similar manner, N-(l-butylidene) propylamine is obtained byreacting N-(2-propylidene) propylamine with butyraldehyde, and N-( 1-propylidene) hexylamine is obtained by reacting N-(2-butylidene)hexylamine with propionaldehyde.

Example III This example illustrates the reaction between a ketimine andan alpha, beta-unsaturated aldehyde to produce an aldimine having aconjugated system of double bonds involving three carbon atoms and anitrogen atom.

One mol of methacrolein was mixed with one mol ofN-(1,3-dimethylbutylidene) 1,3-dimethylbutylamine and the mixtureallowed to stand overnight. The mixture was then warmed to 50 C. for 4hours before distillation. on distillation, a fraction weighing 127parts was collected in the temperature range of 46 C. to 50 C. (10 mm.)which proved to be N-(l-methallylidene) 1,3-dimethylbutylamine. Thisamount corresponded to an 83% conversion to product. The latter compoundhad a refractive index (nZO/D) of 1.455 and a specific gravity (/4) of0.7845. At 200 C. N-(l-methallylidene) 1,3-dimethylbutylamine gave a 17%conversion to dimer.

A higher boiling product (747 C. at 0.5 mm.) obtained from theabove-described distillation was identified as N-(1,3dimethylbutyl)2-isopr0pyl-4-methylcyclohexeneimine. Anal. Calcd.: C, 81.63; H, 12.42;N, .95; neut. equiv. 235. Found: 0,8066; H, 12.31; N, 5.82; neut. equiv,238.

Example IV A mixture of 137 parts of N-(1,3-dimethylbutylidene)1,3-dimethylbutylamine and 53 parts of crotonaldehyde was mixed in aglass reaction vessel and allowed to stand overnight. The resultingmixture was then distilled. Over 79 parts of N-(crotylidene)1,3-dimethylbutylamine fit) 10'" was recovered at approximately 55 C.(10 mm. Hg). This yield corresponded to a 63% conversion to product.

In a similar manner, [N-(l-crotylidene) hexylamine is obtained byreacting N-(2-propylidene) hexylamine with crotonaldehyde andN-(l-crotylidene) phenylamine is obtained by reacting N-(2-butylidene)phenylamine with crotonaldehyde.

Example V Approximately two mols of N-(1,3-diinethylbutylidene)1,3-dimethylbutylamine is combined with approximately 2 mols ofbenzaldehycle in a glass reaction vessel. The mixture is allowed tostand overnight and is then heated at 50 C. for 4 hours. Distillation ofthe resulting mixture yields N-(benzylidene) 1,3-dimethylbutylamine.

N-(toluylidene) octylamine is prepared in a similar manner by replacingthe benzaldehyde in the above-described process with tolualdehyde.

Example VI Approximately one mol of N-(2-propylidene) I ootylamine iscombined with approximately one mol of 2-acetyl-1-cyclohexanone in aglass reaction flask at room temperature. After standing for 24 hours,the mixture is heated at 40 C. When the reaction is complete, themixture is distilled to yield 2-(octylimino-lethyl) cyclohexanone.

Err-ample VII A mixture of about 1 mol of N-(2-hexylidene)cyclohexylamine and about 2 mols of tetrahy- .drobenz-aldehyde isallowed to stand overnight. The mixture is then heated at 50 0. when theThis example illustrates the use of the process in preparing cyclicketimines from acrolein and N- (1,3-dimethylbutylidene)1,3-dimethylbutylamine.

One mol of acrolein was mixed with one mole ofN-(1,3-dimethylbutylidene) 1,3-dimethylbutylamine. The mixture warmedslowly but was held at 35-40 C. by cooling for one hour. At this time,the unused N- (1,3-dimethylbutylidene) 1,3-dimethylbutylamine wasremoved by distillation and the residue acidified and extracted withether. The ether extract was discarded. The amines were liberated withsodium hydroxiole and extracted with ether. The ether extract was driedand distilled to give N-(1,3-dimethylbutyl)-2-isopropylcyclohexenimineboiling at 84-5 C. (1 mm). Anal. C'alcd.: C, 81.4; H, 12.3; N, 6.3;neut. equiv. 221. Found: C, 80.9; H, 12.4; N, 6.3; neut. equiv. 224.

I claim as my invention:

1. A process for preparing an imine which comprises contacting aketimine of the formula 11: alkyl and aryl radicalsmontaining-11011116138. than 8 carbon atoms, with a carbonylic, compound of thegroup consisting of monoaldehydes Rad o wherein R3 is an aliphatichydrocarbon radical containing no more than 10 carbon atoms anddiketones of the formula R(|.I7CHT JR wherein one Ris an aliphaticopen-chain hydrocarbon containing from l to 3 carbon atoms and the otherR is an aliphatic open-chain hydrocarbon radicalcontaining no more than6 carbon atoms, and recovering the desired imine product from thereaction mixture.

2. A process for preparing an imine which comprises contacting a ketimirev of the formula R1; RN=C/ R2 wherein R, R1 and Rzare alkyl :radica1s.contain-. ing from 1 to 81 carbon atoms, with; a carbonylic compoundofthe group consisting of monoaldehydes nv R:(|J=O wherein R3 is analiphatic hydrocarbon radical containing no more than 10 carbon atomsand diketonesiof the formula I! ll RVCCH2CR.

wherein one Ris an aliphatic, open-chain hydroa carbon containing from 1to 3 carbon atoms and the other R is an aliphatic open-chain hydrocarbonradical containingno more than 6 carbon atoms, ina molar1 ratiovarying"from 3:1 to 1:3 at atemperature between 20 C. and 100 0., andsubsequently recovering the desired imine product-from the reactionmixture.

3. A process for preparing an mine which; comprises contacting aketimine of the formula tion proceeding in an exothermic manner onmixing the reactants and without the necessary application of heat, and,subsequently recovering the desired imine product from the reactionmixture.

4. The method as defined in claim 3 wherein the monoaldehyde reactant ismethacrolein.

5. Themethod as defined in claim 3 wherein the monoaldehyde reactant isisobutyraldehyde.

6. The method as defined in claim 3 wherein the monoaldehyde reactant iscrotonaldehyde.

7. The method as defined in claim 3 wherein the monoaldehyde reactant isacrolein.

8:, A, process; for preparing" an; iminea whicltr comprises contacting aketim-ine of 113118; formula,

i., RN=O.

R2 wherein R, R1 and R arealkylradicals containing from 1 to 8 carbonatoms; with a diketone of; theformula wherein'one R is analiphaticopen-chain-hydrocarbon containing from 1' to 3 carbon-atoms-andtheother- R is an aliphatic open-chain hydrocarbon radical containing nomore than 6 car bon atoms-ina molar ratio varying from-321 m 1:3,whereby there is an exchange of-the- -alky1i-- done-group in the saidketimine molecule-ionthe hydrocarbon group attached tothe ca-rbonylicoxygen-atom throughdoublebonds in the--diketone reactant to formaketo-substituted -ketimine and a monoketone, said reactionproceedinginan exothermic manner onmixing the reactants and without the necessaryapplication of heat, and subsequently recovering; the desiredketo-substituted ketimine' product from the re:- action mixture.

Themethod as definedin claim 8*wherein the diketone reactant isacetylacetone:

10. The method as defined in'claim 8"whereinwherein R3 is analiphatic,hydrocarbon;radical containing no;,more;than; 10: carbon,atQmSrat artemperaturebetween 2Q? C. and= ?,'C. where:-

by- ,thereii n xch n f the alkylid ne roup; in the; said-ketiminereactant: for .1 the group the monoaldehyde which is; attached; throu ha;

double -bond to the oxygen; atom so as ;to; :form

n dim d a ke n tprlo cti ndssubse quently removing the aldi-minafrom-the, reaction;

mixture.

Number Name Date;

1,619,953 North ,M,ar. 8,1927. 1,539,957 North Aug. 23, 1927 1,726,713;North; Sept. 3, 1929 1,780,145, Powers Oct; 28,;1930 2,319,848.; Clark;May 25,.1943 2,421,937 Haury June 10, 194 1 2,535,922 Haury Dec. 26-,1950 FOREIGN PATENTS Number Country Date 365,214 Great Britain Jan. 21,1932;

1. A PROCESS FOR PREPARING AN IMINE WHICH COMPRISES CONTACTING AKETIMINE OF THE FORMULA